Multi-dimensional measuring system

ABSTRACT

A laser based tracking unit communicates with a target to obtain position information about the target. Specifically, the target is placed at the point to be measured. The pitch, yaw and roll movements of the target, and the spherical coordinates of the target relative to the tracking unit are then obtained. The target can be, for example, an active device incorporated into a moveable device such as a remote controlled robot.

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 11/761,147 filed Jun. 11, 2007, which is adivisional application of co-pending U.S. patent application Ser. No.10/646,745 filed Aug. 25, 2003, which claims priority to U.S.Provisional Patent Application No. 60/405,712 filed Aug. 26, 2002, allof which are hereby incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the invention

The present invention relates generally to a measuring system. Inparticular, the systems and methods of this invention are directedtoward a multi-dimensional laser tracking system.

2. Background of the Invention

Precision measuring systems have a wide variety of applications. Forexample, in robotics, accurate positioning and orientation of a robot isoften required. To achieve a high degree of precision, a robot positionmeasuring system can be used. Such a system typically uses a laser beaminterferometer to determine the position and/or orientation of anend-effector of the robot. Such system can monitor the position andorientation of the robot end-effector in real-time while providingaccuracy, speed and measurement data.

For example, a Three and Five Axis Laser Tracking System is discussed inApplicant's U.S. Pat. No. 4,714,339, and a Five-Axis/Six-Axis LaserMeasuring System is discussed in Applicant's U.S. Pat. No. 6,049,377,both of which are incorporated herein by reference in their entirety. inaddition, Applicant's U.S. Application No. 60/377,596, entitled “NineDimensional Laser Tracking System and Method,” which was filed on May 6,2003, is also incorporated herein by reference in its entirety toprovide additional description for the present invention.

BRIEF SUMMARY OF THE INVENTION

One aspect of the invention provides multi-dimensional measuring systemthat includes a tracking unit, a target, a distance determining module,and an output module. The tracking unit emits laser light and performstracking using spherical coordinates. The target is in communicationwith the tracking unit. The target is capable of making pitch, yaw, androll movements. The distance determining module determines a distancebetween the tracking unit and the target. The output module outputsposition information about the target relative to the tracking unitbased on the spherical coordinates, the pitch, yaw and roll movements,and the distance.

Preferably, the system further includes an output device that outputsthe position information about the target. Preferably, the roll movementis based on at least one of a comparison between a horizontallypolarized component of the laser light and a vertically polarizedcomponent of the laser light. Preferably, the system further includes afirst photodetector that detects the horizontally polarized component ofthe laser light and a second photodetector that detects the verticallypolarized component of the laser light. Preferably, the system furtherincludes a roll determination circuit that receives an output of thefirst photodetector and an output of the second photodetector. In analternative embodiment, the system uses an electronic level to measureroll movements of the target.

Preferably, the target is an active target that is capable of movingrelative to the tracking unit. Preferably, the target is at least one ofincorporated into a remote unit, fixably attached to an object, used forfeedback control, used for calibration, used for machine tool control,used for parts assembly, used for structural assembly, and used fordimensional inspection. Preferably, the remote unit is a robot.Preferably, the robot includes a drive system and one or more tractiondevices that allow the robot to adhere to a surface. Preferably, thetraction devices are suction cup type devices. Alternatively, a positiveair pressure system can be used to maintain the remote unit movablyattached to the surface. Preferably, the system further includes avacuum system. Preferably, the system further includes one or moreaccessories that allow a function to be performed based at least on theposition information of the target.

Another aspect of the invention provides a remote unit associated with amulti-dimensional measuring system. The remote unit includes a targetand probe assembly coupled to the target. The target is in communicationwith a tracking unit of the multi-dimensional measuring system. Thetarget is capable of making pitch, yaw, and roll movements. The probeassembly includes a probe tip, a probe stem, and a probe base. The probetip is configured to reach locations that are not in a line of sightbetween the tracking unit and the target.

Preferably, the remote unit further includes one or more encoderscoupled to the probe assembly. Preferably, at least one of the encodersis configured to determine a first angular position of the probe tiprelative to the probe base. Preferably, at least one of the encoders isconfigured to determine a second angular position of the probe tiprelative to the probe base. Preferably, at least one of the encoders isconfigured to determine an axial position of the probe tip relative tothe probe base.

Preferably, the remote unit further includes a trigger configured toeffect one or more measurements associated with a location touched bythe probe tip. Alternatively, the remote unit can include a touch sensorassociated with the probe tip. One or more measurements associated witha location is taken when the touch sensor comes into contact with thelocation.

In another aspect, the invention relates to a target associated with amulti-dimensional measuring system. The target includes aretro-reflector and a laser light sensor. The retro-reflector has anapex. The apex is configured to allow at least part of a laser beamlight entering the retro-reflector to exit the retro-reflector. Thelaser light sensor is configured to detect the at least part of thelaser beam light exiting the retro-reflector through the apex.Preferably, the target is configured to be coupled to an opticalmeasuring sensor.

The retro-reflector is preferably a hollow retro-reflector. Theretro-reflector includes an aperture at the apex. The aperture isconfigured to allow the at least part of the laser beam light to exitthe retro-reflector. Preferably, the retro-reflector includes threemirrors that form the apex.

The retro-reflector may alternatively be a solid retro-reflector. Theapex of the solid retro-reflector includes a small flat surface polishedto allow the at least part of the laser beam light to exit theretro-reflector.

The laser light sensor can be a photodetector. Alternatively, the laserlight sensor can be a charge coupled device array sensor. Preferably,the laser light sensor is operable to detect at least one of the pitchand yaw movements of the target.

Another aspect of the invention provides a method for measuring aposition of an object. Exemplary steps of the method includes: (1)monitoring spherical coordinates of a laser light emitting trackingunit; (2) monitoring pitch, yaw, and roll movements of a target incommunication with the tracking unit; (3) determining a distance betweenthe tracking unit and the target; and (4) outputting positioninformation about the target relative to the tracking unit based on thespherical coordinates, the pitch, yaw, and roll movements, and thedistance. It is noted that the method does not necessarily have tofollow the order described above.

Preferably, the roll movement is based on at least one of a comparisonbetween a horizontally polarized component of a laser light emitted bythe tracking unit and a vertically polarized component of the laserlight. Preferably, a roll determination circuit performs the comparisonbetween the horizontally polarized component of the laser light and thevertically polarized component of the laser light.

In another aspect, the invention includes a system for measuring theposition of an object that includes: (1) means for monitoring sphericalcoordinates of a laser light emitting tracking unit; (2) means formonitoring pitch, yaw, and roll movements of a target in communicationwith the tracking unit; (3) means for determining a distance between thetracking unit and the target; and (4) means for outputting positioninformation about the target relative to the tracking unit based on thespherical coordinates, the pitch, yaw, and roll movements, and thedistance.

Accordingly, in accordance with an exemplary embodiment of theinvention, aspects of the invention relate to a multi-dimensionalmeasuring system.

An additional aspect of the invention relates to determining rollmovements of a target based on measurements from a polarized laser.

Additionally, aspects of the invention relate to the design and use ofan active target in conjunction with a tracking unit.

Additionally, aspects of the invention relate to the use of target on aremote unit coupled with a trigger or a touch sensor.

Additional aspects of the invention relate to a remotely controlledrobot that incorporates active target technology.

Additional aspects of the invention relate to a retro-reflector beingused in a target of a multi-dimensional measuring system.

Additional aspects of the invention relate to methods for calibrating avector of a probe tip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an exemplarymulti-dimensional measuring system of the invention.

FIG. 2 is a schematic diagram illustrating a roll determination systemof the invention.

FIG. 3 is a schematic diagram illustrating an exemplary pitch, yaw,roll, and distance measuring system of the invention.

FIG. 4 is a schematic diagram illustrating an exemplary remote unitincorporating an exemplary target of the invention.

FIG. 5 is a schematic cross-sectional view of an exemplary remotecontrolled robot of the invention.

FIG. 6 is a flowchart illustrating an exemplary method of takingmeasurements according to the invention.

FIG. 7 is a schematic diagram illustrating an exemplarymulti-dimensional measuring system of the invention that includes anexemplary tracking unit and an exemplary remote unit.

FIG. 8 is a schematic diagram illustrating another exemplary remote unitof the invention.

FIG. 9 is a schematic diagram illustrating an exemplary probe assemblyof the invention.

FIG. 10 is a schematic diagram illustrating another exemplary probeassembly of the invention.

FIG. 11 is a schematic diagram illustrating another exemplary probeassembly of the invention.

FIG. 12 is a schematic diagram illustrating an exemplary remote unit ofthe invention.

FIG. 13 is a schematic diagram illustrating a front view of theexemplary remote unit shown in FIG. 12.

FIG. 14 is a two-dimensional schematic diagram showing another exemplaryembodiment of a target of the invention that includes a retro-reflector.

FIG. 15 is a three-dimensional schematic diagram showing the exemplaryembodiment of FIG. 14.

FIG. 16 is an exemplary hollow retro-reflector of the invention.

FIG. 17 is an exemplary solid retro-reflector of the invention.

FIG. 18 is a schematic diagram showing another exemplary embodiment of aremote unit of the invention that includes an optical measuring sensor.

FIG. 19 is a schematic diagram showing an exemplary system forestablishing the vector of a probe tip relative to an origin of a targetassociated with the probe tip.

FIG. 20 is a flowchart illustrating an exemplary method of establishingthe vector of the probe tip depicted in FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

The systems and methods of this invention employ a combination of atracking unit and a target to accomplish multi-dimensional lasertracking. For example, in a six-dimensional (6-D) system of theinvention, the six dimensions are pitch, yaw, and roll movements of atarget, and the spherical coordinates, i.e., the 2 angles α, θ and theradial distance, of the target relative to the tracking unit. The targetis preferably an active target, which can be held by a person, a robot,or another moving object. By using an active target, target coordinatesmaintain a relatively perpendicular relation to the incoming beamoriginated from the tracking unit. Additionally, by employing anabsolute distance measurement (ADM) technique, absolute ranging ispossible.

In general, the pitch and yaw based measurements can be derived from anencoder present on the target. The roll measurements can be based on,for example, a polarization or an electronic level technique discussedbelow. The absolute distance measurements or ADM can be accomplishedusing, for example, repetitive time of flight (RTOF) pulses, a pulsedlaser, phase/intensity modulation, or the like. Additional descriptioncan be found in Applicant's U.S. Patent Application No. 60/377,596, theentirety of which is incorporated herein by reference.

Specifically, an RTOF based system includes a photodetector, such as aPIN photodetector, a laser amplifier, a laser diode., and a frequencycounter. A first laser pulse is fired to the target. Upon detecting thereturn pulse, the detector triggers the laser amplifier and causes thelaser diode to fire a second pulse, with the pulses being detected bythe frequency counter. However, it is to be appreciated that the reverselogic also works with equal success. The distance (D) of the target fromthe tracking unit can then be calculated by:$D = {\frac{C}{4}\left( {\frac{1}{f} - \frac{1}{f_{0}}} \right)}$such that:D=0;f=f₀where C is the speed of light, f₀ is a reference frequency and f is thefrequency of the pulses.

The systems and methods of this invention have various applications. Ingeneral, the systems and methods of this invention allow the monitoringof multiple degrees (e.g. six degrees) of freedom of an object. Forexample, the systems and methods of this invention can be used forstructural assembly, real-time alignment and feedback control, machinetool calibration, robotic position control, position tracking, millingmachine control, calibration, parts assembly, dimensional inspection orthe like.

Additionally, the systems and methods of this invention, using a 6-Dtracking system, lend themselves to use in the robotic arts. Forexample, the 6-D laser tracking system can be incorporated into a robot,that is, for example, capable of scaling various objects such that, forexample, precise measurements can be taken of those objects and/orvarious functions performed at specific locations on the object.

FIG. 1 is a schematic diagram illustrating an exemplarymulti-dimensional measuring system of the invention. Laser trackingsystem 10 includes tracking unit 100 and target 150. Tracking unit 100emits one or more lasers 110 that communicate with target 150 todetermine the six dimensional measurements associated with target 150.The six dimensional measurements are output on output device 200. Inparticular, the six dimensions illustrated in FIG. 1 are pitch, yaw, androll movements of target 150, the spherical, and once convertedCartesian, coordinates of target 150 relative to tracking unit 100, andthe radial distance between target 150 and tracking unit 100.

As discussed in Applicant's previous patents and patent applicationreferenced above, the pitch, yaw, and spherical coordinate measurementscan be based on various technologies. The pitch and yaw measurements canbe based on, for example, one or more rotary encoders. The distancemeasurements can be based on, for example, a pulsed laser configuration,an RTOF pulse, phase and/or intensity modulation of the laser beam, orthe like. These various systems can provide absolute ranging of target150. Target 150 is preferably an active target. Specifically, anabsolute distance measurement (ADM) technique can be used to determinean approximate initial distance and then an interferometer basedtechnique can be used to refine the initial distance measurement. TheADM technique is desirable because without it, two measurements must betaken and reverse triangulation must be performed to calculate thedistance.

Tracking unit 100 and target 150 can be, for example, motorized unitsthat allow one or more portions of tracking unit 100 and target 150 tomaintain a perpendicular orientation to incoming laser beam 110 emittedfrom tracking unit 100. Tracking unit 100 is the laser source. Thus,through a combination of rotary encoders and motors that employ positionsignals from one or more photodetectors, as discussed hereinafter,target 150 is capable of remaining perpendicular to incoming laser beam110. For example, through the use of a gimbal type mount andcorresponding position motors, such as stepping motors, servo motorsand/or encoders, target 150 “tracks” tracking unit 100. Based upon therelationship of target 150 to incoming laser 110, 6-D laser trackingsystem 10 is able to determine the orientation of target 150.Alternatively, target 150 can be a passive device, for example, ahand-held device such as a corner cube, for which a user would beresponsible for maintaining a line of sight between target 150 andtracking unit 100.

Preferably, tracking unit 100 is also capable of being miniaturized byincorporating both the absolute distance measurement and interferometerelectronics in, for example, the gimbaled portion of tracking unit 100.This provides various exemplary advantages including reduced weight,reduced size, minimization of external connections, quicker trackingspeeds, and the like.

Output device 200, connected to one or more of tracking unit 100 andtarget 150 via a wired or wireless link 5, outputs position informationassociated with target 150. For example, output device 200 can be acomputer, a feedback input for a position control device, a display, aguidance system, or the like. In general, output device 200 can be anydevice capable of outputting the position information associated Withtarget 150.

Additionally, one or more lasers 110 can be used to communicate theposition information about target 150 back to tracking unit 100. Forexample, after an initial distance is determined, the laser used for theabsolute distance measurement can be used for data communication and theinterferometer based laser used for the radial distance measurements.Alternatively, a dedicated laser can be incorporated into system 10 thatwould allow full time communication between target 150 and tracking unit100.

FIG. 2 is a schematic diagram illustrating a roll determination systemof the invention. In particular, the system includes a laser source (notshown) located in tracking unit 100, polarized laser beam 210,polarizing beam splitter 220, first photodetector 230, secondphotodetector 240, and roll determination circuit 250. Rolldetermination circuit 250 can be, for example, a differential amplifier.The laser source can be, for example, a laser head. As shown in FIG. 2,polarizing beam splitter 220, first photodetector 230, secondphotodetector 240, and roll determination circuit 250 are members oftarget 150.

In operation, tracking unit 100 emits polarized laser beam 210 that isreceived by polarizing beam splitter 220. Polarizing beam splitter 220splits incoming beam 210 into two paths. A first path is directed towardfirst photodetector 230 and a second path of polarized laser beam 210 isdirected toward second photodetector 240. When polarized laser beam 210encounters polarizing beam splitter 220, polarized laser beam 210 issplit into horizontally polarized component 214 and vertically polarizedcomponent 213 as a result of the properties of beam splitter 220.

Horizontally polarized component 214 of beam 210 passes throughpolarized beam splitter 220 to photodetector 240 that generates anoutput signal corresponding to the intensity of horizontally polarizedcomponent 214 of beam 210. Similarly, vertically polarized component 213of beam 210 is directed by beam splitter 220 onto photodetector 230 thatalso produces a signal corresponding to the intensity of verticallypolarized component 213 of beam 210. The intensity measurements ofphotodetectors 230 and 240 can be connected to, for example, thepositive and negative inputs, respectively, of roll determinationcircuit 250, which provides an output signal representative of the rollbetween tracking unit 100 and target 150. Preferably, roll determinationcircuit 250 is a high-gain differential amplifier.

As discussed above, polarized laser beam 210 is split into two differentpolarized components based on the exact roll orientation betweentracking unit 100 and target 150. At a 45° roll orientation,photodetectors 230 and 240 receive the same intensity. However, astarget 150 is rolled in either direction, one of the detectors receivesa greater intensity of polarized laser beam 210 than the other. Thedifference between these outputs is measured by, for example, rolldetermination circuit 250, to provide an indication of the roll. Thissubtraction operation of roll determination circuit 250 alsoadvantageously compensates for background and extraneous noise, such asthat produced by fluctuations in the beam intensity and/or backgroundlight.

Specifically, variations in the beam output, as well as other signalnoise that maybe present, can be measured by both photodetector 230 andphotodetector 240. These variations can be negated by the operation ofroll determination circuit 250. This, for example, increases thesensitivity and accuracy of the system.

The signal representative of the roll can be output to, for example, acomputer (not shown) provided with software that is capable ofrecording, analyzing or initiating further action based on the rollmeasurement.

Alternatively, other techniques may be used for roll determination.These techniques include, but are not limited to, electronic levels,such as pendulum based techniques, conductive fluid capillary tubetechniques, liquid mercury reflective sensors, or, in general, anytechnique that allows the roll of the target to be determined.

FIG. 3 is a schematic diagram illustrating an exemplary pitch, yaw,roll, and distance measuring system of the invention. In particular,components of 6-D laser tracking system 30 include a laser sourcepresent in tracking unit 100, polarized laser beam 310, beam splitter320, corner cube 330, concentrator lens 340, two-dimensionalphotodetector 350, first photodetector 230, second photodetector 240,polarizing beam splitter 220, and roll determination circuit 250.

In operation, the laser source in tracking unit 100 emits polarizedlaser beam 310 that is split by beam splitter 320 into three paths 324,323, and 322 directed toward concentrator lens 340, corner cube 330, andpolarizing beam splitter 220, respectively.

Path 322 of beam 310 reflected by beam splitter 320 and directed towardpolarized beam splitter 220 is used to determine the roll measurements,as discussed above. The combination of the roll, the pitch, and the yawmeasurements made by target 150, along with the spherical coordinatesassociated with tracking unit 100, allows system 30 to obtain thesix-dimensional tracking of target 150.

Path 323 of polarized laser beam 310 passing directly through beamsplitter 320 is reflected by corner cube 330 and returned to trackingunit 100. Tracking unit 100, as discussed in Applicant's related patentsreferenced above, is then able to determine the distance between target150 and tracking unit 100. However, it is to be appreciated that anymethod of determining an absolute distance measurement can be used withequal success with the systems and methods of this invention.

Path 324 directed towards concentrator lens 340 is focused ontotwo-dimensional photodetector 350 from which the pitch and yaw signalsthat drive the motors for target 150 are derived. In particular, astarget 150 moves relative to the laser source in tracking unit 100,laser path 324 directed through concentrator lens 340 moves relative totwo-dimensional photodetector 350. This movement can be detected and acorresponding signal representative of the pitch and/or yaw measurementcan be obtained. Then, as discussed above, the pitch and/or yawmeasurements can be used to control one or more motors on target 150 tomaintain the perpendicular orientation of target 150 to tracking unit100.

FIG. 14 is a two-dimensional schematic diagram showing another exemplaryembodiment of a target of the invention that includes a retro-reflector.FIG. 15 is a three-dimensional schematic diagram showing the exemplaryembodiment of FIG. 14.

System 1400 of the invention includes tracking unit 100 and target 1450.Tracking unit 100 is the source of laser beams that are detectable bytarget 1450. Target 1450 includes retro-reflector 1420 and laser lightsensor 1430. Laser light sensor 1430 can be, for example, aphotodetector, such as photosensor 240 described above, or a chargecoupled device (CCD) array sensor described below. Amplifier/repeater1440 can be associated with laser light sensor 1430 to amplify analogsignals or digital signals produced by laser light sensor 1430.

A laser beam light from tracking unit 100 that go through aperture 1422of retro-reflector 1420 can be detected by laser light sensor 1430.Retro-reflector 1420 can be a hollow retro-reflector or a solidretro-reflector. Apex 1422 allows at least part of laser beam 1410 to gothrough to fall or focus onto laser light sensor 1430, which can be aphotodetector or a CCD array sensor.

Preferably, retro-reflector 1420 is a hollow retro-reflector as shown inFIG. 16. Exemplary hollow retro-reflector 1600 shown in FIG. 16 includesthree mirrors 1610, 1620, and 1630 that are positioned perpendicular toeach other. A common extremity associated with mirrors 1610, 1620, and1630 forms apex 1601 of hollow retro-reflector 1600. Aperture. 1602 ispreferably a tiny hole located at apex 1601 of hollow retro-reflector1600. Aperture 1602 allows at least part of laser beam 1410 to gothrough to fall or focus onto laser light sensor 1430, which can be aphotodetector or a CCD array sensor.

If a solid retro-reflector is used, a small flat surface near the apexis polished to create a way to allow at least part of laser beam 1410 togo through to fall or focus onto laser light sensor 1430. As shown inFIG. 17, solid retro-reflector 1700 includes flat surface 1702 at apex1701. Flat surface 1702 behaves similarly to aperture 1602 describedabove.

Retro-reflector 1420 and laser light sensor 1430 are configured tomeasure the pitch (see axis y-y in FIG. 15) and yaw (see axis x-x inFIG. 15) orientations or movements of target 1450. Vectors V_(y) plusV_(x) and distance D give angle position of incoming laser beam 1410 totarget 1450. Target 1450 can be associated with a remote unit (e.g.,robot 400, remote units 700, 800, and 1200 shown in FIGS. 4, 7, 8, and12, respectively).

FIG. 14 schematically illustrate how a yaw movement associated withtarget 1450 can be measured. When target 1450 indicates no yaw movement,laser beam light 1410 goes through aperture 1422 and is detected bylaser light sensor 1430 at an origin or reference point 1432. However,as indicated by laser paths 1413 and 1415, any yaw movement of target1450 would result in laser beam light 1410 to be detected by laser lightsensor 1430 at locations other than reference point 1432, for example,at points 1433 and 1435, for paths 1413 and 1415 of laser beam light1410, respectively. Note that points 1433, 1432 and 1435 would be alongaxis x-x shown in FIG. 15. Preferably, retro-reflector 1420 and laserlight sensor 1430 are configured to detect a large range of yawmovements. For example, retro-reflector 1420 and laser light sensor 1430can measure yaw movements up to at least about 30 degrees, depending onsize and other factors.

Similarly, the pitch movement of target 1450 can be detected andmeasured using retro-reflector 1420 and laser light sensor 1430. At azero pitch movement, laser beam light 1410 goes through aperture 1422and is detected by laser light sensor 1430 at reference point 1432. Ifthere is a pitch movement, a different part of laser light sensor 1430,either above or below reference point 1432 in a direction perpendicularto the page, would detect the laser beam light. Note that these pointswould be along axis y-y shown in FIG. 15.

As discussed above, laser light sensor 1430 can be a photodetector. In adifferent embodiment of the invention, a CCD array sensor can be used aslaser light sensor 1430. As known in the art, a CCD array sensor caninclude multiple pixels arranged in an array. Preferably, a CCD arraysensor in accordance with the invention includes about 1,000 by 1,000pixels. Larger or smaller number of pixels may also be used. Digitaloutput from the CCD array sensor can processed by a correspondingrepeater 1440. The CCD array sensor is used to detect one or both yawand pitch movements of target 1450. The use of CCD array sensor fordetection of light is known in the art, for example, in digital cameras.Therefore, no further description is believed to be warranted here.

Inclusion of retro-reflector 1420 and laser light sensor 1430 in target1450 as described above provides several advantages. For example, aremote unit (e.g., one of remote units 700, 800, and 1200) associatedwith retro-reflector 1420 can be more functional in an upside-downorientation, which is otherwise not possible. In addition, the use ofretro-reflector 1420 allows a target and/or a remote unit of theinvention to be smaller in size and/or lighter in weight.

FIG. 4 illustrates an exemplary remote unit of the invention. Robot 400includes a plurality of suction cup type devices 410, drive mechanism420, controller 430, accessory 440, suction device 450, and a target.The target can be, for example, one of target 150 and target 1450. Robot400 also includes various other components such as a power supply,battery, solar panels, or the like that have been omitted for the sakeof clarity and would be readily apparent to those of ordinary skill inthe art.

In operation, the combination of target 150 in conjunction with robot400 allows, for example, precise movement and location tracking of robot400. While a particular robotic active target is discussed below, it isto be appreciated that in general the target can be fixably attached toany object to allow monitoring of up to six degrees of freedom of theobject, or, alternatively, the target can be attached to a movabledevice and the position of that device monitored.

Suction cup type devices 410 are connected to suction device 450 via,for example, hoses (not shown) that enable robot 400 to remain affixedto a surface. For example, controller 430, in conjunction with suctiondevice 450 and suction cup type devices 410 can cooperate with drivesystems 420 such that robot 400 is able to traverse a surface. Forexample, suction cup type devices 410 and drive mechanism 420 cancooperate such that sufficient suction is applied to suction cup typedevices 410 to keep robot 400 affixed to a surface, while still allowingthe drive mechanism 420 to move the robot 400 over the surface. Forexample, drive mechanism 420 can include four wheels, and associateddrive and suspension components (not shown). The wheels allow thetraversal of robot 400 over a surface while maintaining the rotationalorientation of robot 400 relative to tracking unit 100. However, ingeneral, while it is simpler to operate robot 400 such that therotational orientation remains constant relative to tracking unit 100,the system can be modified in conjunction with the use of the polarizedlaser to account for any rotational movement that may occur.Specifically, for example, the rotational movement of robot 400 can bealgorithmically “backed-out” of the orientation measurements based onthe polarized laser to account for any rotation of robot 400.

Furthermore, it should be appreciated that while robot 400 includessuction device 450 and suction cup type devices 410, any device, orcombination of devices, that are capable of movably fixing robot 400 toa surface would work equally well with the systems and methods of theinvention. For example, a positive air pressure system can be used toforce robot 400 to be movably fixed to the surface. For example, thepositive air pressure system can include an air blowing unit that blowsair downwards when robot 400 is traversing under, rather than above, thesurface. The downward air movement keeps robot 400 movably fixed underthe surface. Additionally, depending on the surface type, a magnetic,gravitational, resistive, or the like type of attachment system could beemployed.

Controller 430, which can, for example, be in wired or wirelesscommunication with a remote controller (not shown), allows fornavigation of robot 400 in cooperation with drive mechanism 420. Forexample, drive mechanism 420 can include a plurality of electric motorsconnected to drive wheels, or the like.

Accessory 440, can be, for example, a marking device, a tool, such as adrill, a painting attachment, a welding or cutting device, or any otherknown or later developed device that needs precise placement on asurface. The accessory can be activated, for example, remotely incooperation with controller 430. In addition, accessory 440 can includea vacuum system.

Since accessory 440 is located on a known distance from target 150, theexact position of accessory 440 is always known. Thus, a user canposition accessory 440 in an exact location such that accessory 440 canperform an action at that location. For example, a local effect sensorlike a strip camera, a Moire fringe patent sensor, or a touch probe canbe attached to the end of target 150. Tracking unit 110 combined withtarget 150 can provide the orientation of the local sensor in a spatialrelationship with the part to be measured while the local sensor ismeasuring the contours of a part, such as a car body, a building, a partin an environmentally hazardous area, or the like.

FIG. 5 illustrates an exemplary schematic, cross-sectional view of robot400. In this illustration, robot 400 is shown to include movabledistance determining device 540. In addition to position sensingequipment associated with target 150, movable distance determiningdevice 540 extends from the base of robot 400 to surface 510. Distancedetermining device 540 measures the exact distance between target 150and surface 510 such that the exact location of the surface 510 relativeto target 150 is always known.

As illustrated in FIG. 5, suction cup type devices 410 are located afixed distance above surface 510 via spacers 530. For example, spacers530 can be a bearing, or other comparable device that allows for suctioncup type devices 410 to remain a fixed distance above surface 510 whilestill allowing air 520 to create a suction between robot 400 and surface510.

Given the mobility of robot 400, it is foreseeable that robot 400 maynot always be in communication with tracking unit 100. In the eventrobot 400 loses line-of-sight with tracking unit 100, the 6-D lasertracking system can then enter a target acquisition mode.

In the target acquisition mode, a user can, for example, with ajoystick, aim tracking unit 100 generally in the vicinity of robot 400.Tracking unit 100 then commences a target acquisition process in whichtracking unit. 100 begins a spiral type pattern that spirals outward tolocate target 150. Upon acquisition of target 150, communication betweentracking unit 100 and target 150 is established and the six-dimensionalmeasurements are again available.

Alternatively, for example, target 150 can maintain communication withtracking unit 100 via, for example, a radio communication link, or otherknown or later developed system that allows the tracking unit 100 totrack the relative position of target 150 regardless of whetherline-of-sight is present. Thus, when line-of-sight is reestablished, asdiscussed above, the six-dimensional measurements are available.

FIG. 6 is a flowchart illustrating an exemplary method of takingmeasurements according to the invention. In particular, control beginsin step S100 where communication between a tracking unit (e.g., trackingunit 100) and a target (e.g., target 150) are established. For example,for an interferometer based system, the target can be placed at a knownposition to both establish communication with the tracking unit as wellas to initialize the system. For an absolute distance measurement systemthe target is placed in communication with the laser and an approximateradial distance (R) obtained.

Next, in step S120, the target is placed at a first point to bemeasured.

Then, in step S130, the pitch, yaw, roll, and spherical coordinates areobtained.

In step S140, the spherical coordinates are converted to Cartesian(x,y,z) coordinates, where x is the horizontal position, y the in/outposition, and z the up/down position of the target.

Then, in step S150, the position measurements are output.

Control then continues to step S160 in which a determination is made onwhether additional points should be measured. If so, the process goes tostep S170; otherwise, the process ends.

In step S170, the target is moved to a new point to be measured. In anembodiment in which the target is coupled to a remote unit such as arobot, the robot is commanded to move to the new point. The process thenreturn to step S130.

There may be instances, for example, where the point to be measured isnot in the line-of sight of the tracking unit, or, alternatively, forexample, the point to be measured is inaccessible by the target. FIGS.7-13 illustrate exemplary embodiments in which a probe assembly isassociated with the target in a remote unit to take measurements atpoints that is otherwise inaccessible by the target.

FIG. 7 is a schematic diagram illustrating an exemplarymulti-dimensional measuring system of the invention that includes anexemplary tracking unit and an exemplary remote unit. Multi-dimensionalmeasuring system 70 includes tracking unit 100 and remote unit 700.Remote unit 700 includes target 150, probe assembly 600. Probe assembly600 includes probe stem 610, probe tip 620, and probe base 730. Remoteunit 700 is configured to obtain positional information of a point orlocation that is touchable by probe tip 620, but which is not in theline of sight of tracking unit 100.

In this embodiment, target 150, as described above, can make pitch, yaw,and roll movements about origin 760, the position of which can bedetermined because it is in the line of sight of tracking unit 100.Probe 620 is configured to touch or come into contact with a point orlocation that is not in the line of sight of tracking unit. Probe tip620 is connected to probe base 730 by probe stem 610. In one embodiment,probe base 730 is fixed or immovable with respect to target 150. In suchembodiment, probe base 730 itself cannot make any pitch, yaw, or rollmovements. However, probe tip 620 can move pivoting about probe base 730along circle 605, which forms a disc shape point cloud perpendicular tothe page. Thus, in additional to the previously described six dimensionsassociated with target 150, the movement of probe tip 620 adds theseventh dimension, making system 70 a seven dimensional system.

A point or location that is not in the line of sight of tracking unit100, but which is touchable by probe tip 620, can be determined asfollows.

First, probe stem 610 is locked in place relative to probe base 730.Probe stem 610 can be locked in place using a number of differentmethods. For example, probe stem 610 can be locked in place with the useof a wing nut and associated locking teeth 640.

Second, target 150 is brought closer to seat 750 and probe 620 comesinto contact with center 752 of seat 750. Center 752 of seat 750 is aknown location. For example, the position (x, y, z) of center 752relative to tracking unit 100 can be determined using a system andmethod shown in FIGS. 19 and 20, which are described below. Becauseorigin 760 can be measured by tracking unit 100 directly, and center 752of seat 750 has a known position, the vector of point tip 620 relativeto origin 760 is established.

Third, target 150 is moved to measure a point or location that istouchable by probe tip 620. Using computer software or other knownmethods, position information associated with the point or locationtouched by probe tip 620 can be calculated base on the positioninformation of origin 760 and the vector of point 620 relative to origin760.

In lieu of using seat 750 to determine the vector of point 620 relativeto origin 760, one or more encoders coupled to probe base 730 can beused.

FIG. 8 is a schematic diagram illustrating another exemplary remote unitof the invention. Remote unit 800 shown in FIG. 8 includes probeassembly 600 that is configured to move along two axes, which makesremote unit 800, when used with tracking unit 100, an eight-dimensionalmeasuring system. In accordance with this exemplary embodiment, inaddition to target 150, probe assembly 600, remote unit 800 furtherincludes encoders 720 and 740. Optionally, remote unit 800 furtherincludes handle assembly 700 (which includes trigger 710).

In this exemplary embodiment, yaw movements of probe base 730 ismeasured by encoder 720, and pitch movements of probe base 730 ismeasured by encode 740. Thus, in this embodiment, probe tip 620 can bemoved about probe base 730 to establish a spherical point cloud aboutprobe base 730. The vector of probe tip 620 relative to origin 760 canbe established using measurements taken by encoders 720 and 740.

To measure a point or location touchable by probe tip 620, the followingsteps can be used.

First, target 150 is brought near the point or location and probe tip620 is moved about probe base 730 so that probe tip can come intocontact with the point or location. Second, because origin 760 is in theline of sight of tracking unit 100, the six dimensions associated withtarget 150 can be obtained as described above. Third, using informationobtained by encoders 720 and 740, which establishes the vector of probetip 620 relative to origin 760, position information associated with thepoint or location can be obtained. Preferably, the second and thirdsteps can be performed in a single step using by squeezing trigger 710.

FIG. 9 is a schematic diagram illustrating an exemplary probe assemblyof the invention. Exemplary point cloud 607, if projected in threedimensions relative to probe base 730, represents the distance d ofprobe tip 620 from an origin, such as probe base 730.

FIG. 10 is a schematic diagram illustrating another exemplary probeassembly of the invention. In this embodiment, probe stem 610 has an “L”shape configuration rather than a straight “I” shape configuration.However, in general, probe stem 610 can be in any shape and the useronly need adjunct seat 750 such as to allow probe tip 620 to sit in seat750 during initialization to create the point cloud. As depicted in FIG.10, the “L” shape probe stem 610 enables probe tip 620 to touch a bottomsurface of an object, such as bottom surface 1052 of object 1050.

FIG. 11 is a schematic diagram illustrating another exemplary probeassembly of the invention. Probe assembly 1100 and tracking unit 100constitute a nine-dimensional version of an exemplary tracking systemaccording to this invention. In particular, in addition to the movementsof probe stem 610 illustrated in FIGS. 7 and 8, probe stem 610 in FIG.11 is capable of extending in a longitudinal direction, i.e.,telescoping, so that distance d can be varied. With the aid of encoder1000, which can be, for example a glass-scale encoder, a linear scaleencoder, a magnescale encoder, or the like, the length of probe stem 610can be determined.

In operation, a user can either adjust the length or orientations ofprobe stem 610 and perform initialization, with the length of probe stem610 remaining static during measurements, or, in addition to the stepsenumerated above, also vary the length of probe stem 610 duringinitialization to create a semi-solid point cloud (not shown) thatrepresents the distance d of probe tip 620 from an origin relative tothe rotational movement of probe base 730, the length of extension ofprobe stem 610, and the rotational movement of probe tip 620 about probebase 730. The various readings from the encoders 720, 740, and 1000 canthen be stored to be used for actual position determination during themeasurement process.

Then, during use, one or more of probe length, e.g., distance d(measured by encoder 1000), probe rotation in yaw direction (measured byrotary encoder 720), and probe rotation in pitch direction (measured byencoder 740) can be varied by the user as appropriate to allow probe tip620 to be placed on the object to be measured. Furthermore, while probetip 620 is illustrated herein is a sphere, it is to be appreciated thatthe tip can be any shape, such as a point, cup, or bearing that allowsprobe tip 620 to move across an object, or the like. For example, asdiscussed previously, a measurement can be taken instantaneously usingtrigger 710 (see FIG. 8), or continuously, for example, while probe tip620 traverses an object.

FIGS. 12 and 13 are schematic diagrams illustrating different views ofan exemplary remote unit of the invention. Remote unit 1200 includestarget 150 that has been described above. Target 150 includes beamsplitter 1240 and a plurality of photodetectors 1250. Remote unit 1200further includes adjustable probe assembly 1210, electronic level 1220,and handle 1230 Probe assembly 1210 includes probe tip 1260.

The operation of remote unit 1200 involves a user maintaining anorientation between remote unit 1200 and a tracking unit (e.g., trackingunit 100 shown in FIG. 1). Measurements with remote unit 1200 can beaccomplished in a similar fashion to that discussed in relation toremote units 700 and 800 above. Specifically, an initialization isperformed to determine the position of probe tip 1260 in relation toremote unit 1200. The initialization can occur after fixing of probeassembly 1210 in a fixed position or, alternatively, by moving probeassembly 1210 through a plurality of positions and, for example,creating a point cloud as discussed above. Alternatively, probe tip 1260can be placed at various positions on a known object, such as a sphere,and initialization accomplished.

When a measurement associated with a location touched by probe tip 1260is to be taken, a trigger associated with handle 1230 is squeezed.Alternatively, probe tip 1260 can be configured to be touch-sensitive.For example, in an exemplary implementation of the invention, probe tip1260 is associated with a touch sensor. In the exemplary implementation,a measurement is taken by remote unit 1200 whenever probe tip 1260 comesinto contact with the location. In this context, the contact is aphysical contact.

In other implementations, the contact can be effected when probe tip1260 comes into close proximity with the location. Such non-physicalcontact can be accomplished using, for example, magnetic or infrareddevices that are associated with probe tip 1260.

Remote unit 1200 can determine roll based on, for example an electroniclevel technique or, for example, using the differential amplifiertechnique discussed above. The electronic level technique can beimplemented using electronic level 1220.

FIG. 18 is a schematic diagram showing another exemplary embodiment of aremote unit of the invention that includes an optical measuring sensor.Remote unit 1800 includes optical measuring sensor 1830. Opticalmeasuring sensor 1830 can be used to measure an area or a surfacegeometry. Preferably, optical measuring sensor 1830 is located near abottom portion of remote unit 1800, as shown in FIG. 18. However,optical measuring sensor 1830 can be otherwise associated with remoteunit 1800, including near a top or a side portion of remote unit 1800.

FIG. 19 is a schematic diagram showing an exemplary system forestablishing the vector of a probe tip relative to an origin of a targetassociated with the probe tip. System 1900 includes remote unit 700 withorigin 760 and probe tip 620 as described above. Probe tip 620 can be,for example, a ruby sphere. System 1900 further includes magnetic puck1910, spherical mounted retro-reflector (SMR) 1920, and one or bothdummy units 1930 and 1940.

Magnetic puck 1910 includes a plurality of supports 1912, 1914, and1916. Magnetic puck 1910 further includes magnet 1918. Supports 1912,1914, and 1916 are configured to support one of SMR 1920, hemisphericaldummy unit 1930, and spherical dummy unit 1940. Preferably, each of SMR1920 and dummy units 1930, 1940 are made of magnetic stainless steel sothat magnet 1918 of magnetic puck 1910 can secure it on supports 1912,1914, and 1916. Preferably, magnet 1918 is disposed at a location amongsupports 1912, 1914, and 1916.

SMR 1920 includes retro-reflector 1924 that is housed within body 1926of SMR 1920. Retro-reflector 1924 can be a hollow retro-reflector (e.g.,similar to hollow retro-reflector 1600) or a solid retro-reflector(e.g., similar to solid retro-reflector 1700). Body 1926 is preferablymade of magnetic stainless steel. SMR 1920 can have a range ofdiameters. Typical diameters of SMR 1920 are 0.5 inch, 0.75 inch, 1.0inch, and so on. Retro-reflector 1924 includes apex 1922. Preferably,SMR 1920 is configured so that apex 1922 is located at the center of SMR1920.

Hemispherical dummy unit 1930 includes body 1936 and center 1932.Hemispherical dummy unit 1930 has a diameter that is same as thediameter of SMR 1920 so that the location of center 1932 correspond withthe location of apex 1922. Body 1936 is preferably made of magneticstainless steel.

Spherical dummy unit 1940 includes body 1946 and center 1942. Sphericaldummy unit 1940 has a diameter that is same as the diameter of SMR 1920so that the location of center 1942 correspond with the location of apex1922. Body 1946 is preferably made of magnetic stainless steel.

FIG. 20 is a flowchart illustrating an exemplary method of establishingthe vector of the probe tip depicted in FIG. 19.

In step S210, magnetic puck 1910 is fixed to a location, e.g., thelocation of seat 750 shown in FIG. 7, Preferably, magnetic puck 1910 issecured to the location so that placement or removal of SMR 1920 ordummy units 1930, 1940 would not move magnetic puck 1910.

In step S220, SMR 1920 is placed on magnetic puck 1910. Preferably, SMR1920 is secured to magnetic puck 1910 by magnet 1918 on supports 1912,1914, and 1916.

In step S230, position information of apex 1922 can be obtained by atracking unit, e.g., tracking unit 100 shown in FIG. 7. In this manner,SMR 1920 behaves as a target in a conventional three dimensionalmeasurement system.

In step S240, SMR 1920 is replaced with one of dummy units 1930 and 1940on magnetic puck 1910. For example, SMR 1920 is removed and one of dummyunits 1930 and 1940 is placed on magnetic puck 1910, secured by magnet1918 on supports 1912, 1914, and 1916.

In step S250, probe tip 620 is brought to touch the dummy unit toestablish the position information of the center of the dummy unit instep S260.

If hemispheric dummy unit 1930 is used, probe tip 620 touches center1932 of hemispheric dummy unit 1930. Because the diameter of hemisphericdummy unit 1930 is same as the diameter of SMR 1920, the position ofcenter 1932 corresponds with the position of apex 1922, which wasobtained in step S230.

In step S260, the vector of probe tip 620 relative to origin 760 ofremote unit 700 is established. This can be done because, as explainedabove, origin 760 is in the line of sight of tracking unit 100 and probetip 620 touches a known location, which is center 1932, the positionestablished in step S230 by apex 1922.

If spherical dummy unit 1940 is used in step S240, probe tip 620 cannottouch center 1940 directly. However, the position of center 1940 can beestablished by probe tip 620 touching four or more points on body 1946in step S250. Because the diameter of spherical dummy unit 1940 is sameas the diameter of SMR 1920, the position of center 1942 correspondswith the position of apex 1922, which was obtained in step S230. Thevector of probe tip 620 relative to origin 760 can then be establishedin step S260.

In step S270, probe tip 620 can be used to take measurements at variouspoints and locations.

As illustrated in the figures and described above, the multi-dimensionalsystems of the invention can be implemented either on a singleprogrammed general purpose computer, or a separate programmed generalpurpose computer and associated laser generating and detecting, motorand rotary encoder components. However, various portions of themulti-dimensional laser tracking system can also be implemented on aspecial purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hard-wired electronic or logiccircuit such as a discrete element circuit, a programmable logic devicesuch as a PLD, PLA, FPGA, PAL, or the like. In general, any devicecapable of implementing a state machine that is in turn capable ofimplementing the measurement techniques discussed herein and illustratedin the drawings can be used to implement the multi-dimensional lasertracking system according to this invention.

Furthermore, the disclosed methods may be readily implemented insoftware using object or object-oriented software developmentenvironments that provide portable source code that can be used on avariety of computer or workstation hardware platforms. Alternatively,the disclosed multi-dimensional laser tracking system may be implementedpartially or fully in hardware using standard logic circuits or VLSIdesign. Whether software or hardware is used to implement the systems inaccordance with this invention is dependent on the speed and/orefficiency requirements of the system, the particular function, and theparticular software and/or hardware systems or microprocessor ormicrocomputer systems being utilized. The multi-dimensional lasertracking system and methods illustrated herein, however, can be readilyimplemented in hardware and/or software using any known orlater-developed systems or structures, devices and/or software by thoseof ordinary skill in the applicable art from the functional descriptionprovided herein and a general basic knowledge of the computer andoptical arts.

Moreover, the disclosed methods may be readily implemented as softwareexecuted on a programmed general purpose computer, a special purposecomputer, a microprocessor, or the like. In these instances, the methodsand systems of this invention can be implemented as a program embeddedon a personal computer such as a Java® or CGI script, as a resourceresiding on a server or graphics workstation, as a routine embedded in adedicated multi-dimensional laser tracking system, or the like. Themulti-dimensional laser tracking system can also be implemented byphysically incorporating the system and method into a software and/orhardware system, such as the hardware and software systems of amulti-dimensional laser tracking system.

It is, therefore, apparent that there has been provided, in accordancewith the present invention, systems and methods for multi-dimensionallaser tracking. While this invention has been described in conjunctionwith a number of exemplary embodiments, it is evident that manyalternatives, modifications and variations would be or are apparent tothose of ordinary skill in the applicable arts. Accordingly, theinvention is intended to embrace all such alternatives, modifications,equivalents and variations that are within the spirit and scope of thisinvention.

The foregoing disclosure of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be apparent toone of ordinary skill in the art in light of the above disclosure. Thescope of the invention is to be defined only by the claims appendedhereto, and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

1. A target associated with a multi-dimensional measuring systemcomprising: a retro-reflector having an apex, wherein the apex isconfigured to allow at least part of a laser beam light entering theretro-reflector to exit the retro-reflector; and a laser light sensorconfigured to detect the at least part of the laser beam light exitingthe retro-reflector through the apex.
 2. The target of claim 1, whereinthe target is configured to be coupled to an optical measuring sensor.3. The target of claim 1, wherein the retro-reflector is a hollowretro-reflector.
 4. The target of claim 3, wherein the retro-reflectorcomprises an aperture at the apex, the aperture is configured to allowthe at least part of the laser beam light to exit the retro-reflector.5. The target of claim 3, wherein the retro-reflector comprises threemirrors that form the apex.
 6. The target of claim 1, wherein theretro-reflector is a solid retro-reflector.
 7. The target of claim 6,wherein the apex comprises a small flat surface polished to allow the atleast part of the laser beam light to exit the retro-reflector.
 8. Thetarget of claim 1, wherein the laser light sensor is a photodetector. 9.The target of claim 1, wherein the laser light sensor is a chargecoupled device array sensor.
 10. The target of claim 1, wherein thelaser light sensor is operable to detect at least one of the pitch andyaw movements of the target.